core/pci-dt-slots: Fix devfn lookup

We only want to use the device part of the bdfn when looking up the
switch down port. The required bit twiddling happens inside
find_devfn() and the masking here is broken since:

	a) Keeps the fn part of the bdfn, and
	b) Masks off part of the device number.

This breaks looking up the slot information in some cases.

Fixes: 6878b80 ("pci-dt-slot: Big ol' cleanup")
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

core/pci-dt-slot.c

@@ -152,7 +152,7 @@ static struct dt_node *find_node_for_dev(struct phb *phb,
 			return NULL;
 
 		/* find this down port */
-		return find_devfn(sw_up, pd->bdfn & 0x1f);
+		return find_devfn(sw_up, pd->bdfn);
 
 	default:
 		PCIDBG(phb, pd->bdfn,